The invention teaches a process and apparatus to rapidly form a flat or shaped fabric and the fabric formed thereby consisting of groups of yarn densely covering an area.
Textile fabric is often formed from strands, or filaments, of yarn by weaving or knitting or the like to hold the strands together. Processes of weaving and knitting where strands are guided over and under adjacent strands are slow and do not permit much variety in forming fabric shapes. In a loom for weaving fabrics, the weft yarns are added one at a time. These processes typically result in flat or cylindrical fabrics. There is a need for a process that, in addition to making flat or cylindrical fabrics, permits more variety in forming fabrics with random three dimensional shapes, for instance, that would permit forming an article of clothing, such as a shirt, without having to cut pieces of fabric and seam them together. The cutting of fabric into irregularly shaped patterns wastes a lot of fabric, plus cutting and sewing add steps over forming the fabric article directly. The same problem is present in making flexible engineered shapes such as automotive air bags, sail boat sails, industrial filter bags, or the like. In these cases, the need for seams to form three dimensional shapes presents problems with structural strength and/or permeability so the seams must be carefully made.
There is a need for a way to rapidly form a flexible fabric from strands of yarn; there is a need for a way to rapidly form a three dimensional, flexible, fabric article without cutting a flat fabric and seaming.
There is also a problem making complex shapes for composite structures that may be impregnated with a hardenable resin. It is sometimes desired to lay down the filaments in a three dimensional shape before adding the resin or during resin addition. Present means for doing so involve complex forms with retractable support means to hold the filaments in place before the resin hardens. There is a need for a simpler way to preform these fabric shapes without seams. Such seams would compromise the strength of the composite structure.
A series of Oswald patents (U.S. Pat. No. 4,600,456; U.S. Pat. No. 4,830,781; and U.S. Pat. No. 4,838,966) lay down a pattern of partially vulcanized rubber coated strips, or cords, to make a loop of preformed reinforcing belt for a vehicle tire. The strips or cords are stuck together wherever they touch to make a relatively stiff structure. The cords are laid in a xe2x80x9czig-zag repeating pattern with succeeding lengths of the strips being displaced from each other. The cord lengths are interleaved with lengths of cords disposed at an opposite angle. This interleaving relationship results in a woven structurexe2x80x9d. The stickiness of the partially vulcanized rubber apparently holds the cords in place to a forming surface and to each other until the belt is assembled with other elements of the tire and molded under heat and pressure to form a completed tire.
The process practiced by Oswald and others uses one or a few cords that are traversed back and forth across the belt numerous times to complete one circumference. This is believed to result in a multilayered structure where the cords in any one layer are sparsely arrayed, but they do not completely cover the belt area. It is only after repeated zig-zag passes over the belt area that the area becomes sparsely covered with cord. Due to the repeated zig-zag passes of only a few cords, it is believed that within any one layer there are cords layed down in two different directions that do not cross one another. Cords that cross one another would be in different layers. These structural features of the reinforcing belts are symptomatic of a process that lays down only a few cords at a time and must make repeated passes over the belt area to get coverage of the area. There is a need for a simple non-weaving process that can make fabric structures by laying down many yarns simultaneously over a fabric area to sparsely cover it rapidly, and to stack several of such sparse yarn coverages to densely cover the area.
The invention concerns a fabric product and its variations, processes for making the product and variations on such processes and several forms of automated devices for making preferred forms of the product. Included in the invention are the following embodiments:
A fabric structure comprising:
a plurality of groups of yarn densely covering an area and the yarns within one group following substantially parallel paths (defined to include loops in a yarn path) and the yarns in one group arranged to cross yarns in another group;
a plurality of subgroups comprising each group, each subgroup comprising a plurality of yarns sparsely covering said area, and the yarns in one subgroup of one group offset from the yarns in the other subgroups in said one group;
a plurality of connections between the top subgroup of the structure and the bottom subgroup of the structure either directly or through the yarns in other subgroups.
In other embodiments, there are unconnected regions separate from the connections and the inherent flexibility of the yarns in the structure is retained in the unconnected regions.
In other embodiments, the connections are spaced apart bonded regions and there are unbonded regions separate from the bonded regions and the inherent flexibility of the yarns is retained in the unbonded regions.
In further embodiments, the yarns in a subgroup follow substantially parallel paths that cause each of the yarns to cross itself within a subgroup and to cross its neighbors within a group.
In other embodiments, the yarns in a subgroup of one group are folded over to become the yarns in a subgroup of another group and thereby to cross them.
In other embodiments, a film or nonwoven sheet is placed between two adjacent subgroups within the structure.
In other embodiments, there are three groups of yarn employed in the fabric structure to make a stacked triaxial fabric structure.
Also claimed herein is a method of forming such an interlaced structure comprising:
laying down a first yarn subgroup having a plurality of yarns oriented in a first angular direction free of crossings, the yarns in the first subgroup following substantially parallel paths that are spaced apart in a repeating pattern to sparsely cover a predetermined fabric area;
stacking a second yarn subgroup next to the first yarn subgroup, the second yarn subgroup having a plurality of yarns oriented in a second angular direction free of crossings, the yarns in the second subgroup following substantially parallel paths that are spaced apart in a repeating pattern to sparsely cover the predetermined fabric area;
continuing alternately stacking a plurality of first yarn subgroups and a plurality of second yarn subgroups comprising the substeps of:
offsetting the plurality of yarns in any one subgroup of the plurality of first subgroups from the plurality of yarns in all other subgroups of the first plurality of subgroups, and laying down all the yarns in one of the first plurality of subgroups before laying down the yarns in another subgroup;
offsetting the plurality of yarns in any one subgroup of the plurality of second subgroups from the plurality of yarns in all other subgroups of the second plurality of subgroups and laying down all the yarns in one of the second plurality of subgroups before laying down the yarns in another subgroup;
stopping the stacking when all of the plurality of first subgroups form a first yarn group comprising yarns that densely cover the predetermined fabric area, and when the stacking of all of the plurality of second subgroups form a second yarn group comprising yarns that densely cover the predetermined fabric area; and
connecting the yarns in the top subgroup in the stack to the yarns in the bottom subgroup in the stack to thereby contain the other subgroups in the stack and form an interlaced fabric structure.
The method as above further comprising: urging the stacked subgroup of each group to nest together into a consolidated structure where the yarns in one group bend over the yarns in the adjacent groups.
The method as above wherein the connecting step comprises bonding said subgroups at spaced regions and providing unbonded regions separate from the bonded regions wherein the inherent flexibility of the yarns is retained in the unbonded regions.
Connecting the outermost subgroups may also include connecting strands from the innermost subgroups. The connecting means may consist of loops of yarn, spots of adhesive, bonded joints (such as those formed by squeezing the outermost groups together and applying ultrasonic energy to the squeezed yarns), staples and clips.
The invention is also a three dimensional shaped product and a process of rapidly forming a three dimensional shaped fabric where the yarns in the subgroups are not necessarily generally parallel, but are regularly spaced to follow the contours of the shape. The three dimensional, shaped, interlaced, fabric structure, comprises:
a stack of a first plurality of subgroups, a second plurality of subgroups, and a third plurality of subgroups, each subgroup having yarns spaced apart to define a sparse covering of a fabric area, the yarns generally parallel, and the yarns following a curved path in space;
the stacked subgroups arranged in a predetermined array with reference to a common axis and a common reference plane perpendicular to said axis;
the first subgroups arranged at a first angle with respect to said reference plane and positioned at a first rotational angle about said axis, the second subgroups arranged at a second angle with respect to said reference plane and positioned at a second rotational angle about said axis, the third subgroups arranged at a first angle with respect to said reference plane and positioned at a third rotational angle about said axis, wherein the yarns in any one of the first, second and third subgroups cross the yarns in another of the first, second and third subgroups; within each first, second and third plurality of subgroups, the yarns of one subgroup are offset from the yarns of the other subgroups to thereby form a group of yarns for each of the respective subgroups, the group for any respective subgroups densely covering a fabric area;
the top subgroup in the stack is connected to the bottom subgroup in the stack to thereby form a three-dimensional, shaped interlaced, fabric structure.
Further taught herein is a fabric forming device for forming a fabric structure from a plurality of yarns, comprising:
(a) an endless loop conveyor having a traveling support surface for supporting the fabric structure being formed, the surface having opposed edges parallel to the direction of travel and holders along each edge to temporarily hold the yarn to resist lateral motion of the yarn, the conveyor having a controllable motor for propelling the traveling support;
(b) a plurality of guide bars adapted for movement across the surface from edge to edge, each bar containing a plurality of guides for repeatedly guiding a plurality of yarns from the holders along one edge to the holders along the opposed edge and back to the one edge, the guide bars having a controllable actuator for propelling the bars back and forth across the support surface;
(c) a plurality of bonders arranged across the support surface between the support surface edges and beyond the last guide bar in the direction of travel of the surface, the bonders adapted to bond one yarn to another yarn where they cross;
(d) a controller for coordinating the controllable motor; and actuators to continuously form a fabric structure on the support surface of the conveyor.
A further embodiment is a yarn dispensing device for laying down yarn accurately on a compound curvature, when using a mechanical actuator, comprising the following elements:
(a) a mechanical guide actuating means;
(b) a yarn guide comprising a frame that supports a hollow shaft through which yarn can pass;
(c) a slide, attached to the yarn guide, and also attached to the guide actuating means;
(d) a block mounted on said hollow shaft which supports a plurality of flexible springs that intersect at a common point;
(e) at the point of intersection of the springs is a hollow tip with a hemispherical end through which the yarn can pass, said springs permitting motion of the tip in an axial or angular direction, the rotation of said shaft allowing the tip to roll over any surface it contacts while it is also free to deflect axially and angularly, so as to accurately place a yarn on the surface while the yarn passes through a hole in the hollow shaft and a hole in the hollow tip.